This invention relates to a movement detector which outputs pulse-like electrical signals as a moving body moves.
One example of a conventional movement detector is a rotation detector which is designed as follows: In the rotary detector, the moving body is a rotary disk. A number of slit-shaped through-holes, namely, light transmitting parts are formed in the periphery of the rotary disk at predetermined angular intervals while leaving light intercepting parts therebetween. That is, in the periphery of the rotary disk, the light transmitting parts and the light intercepting parts occur alternately, thus forming a slit pattern. On the other hand, a light emitting element such as a light emitting diode is provided to apply light to the slit pattern of the rotary disk, and a light receiving element such as a photo-transistor is provided to receive light passed through the light transmitting parts to output pulse-like electrical signals. The electrical signals are processed to detect the rotation of the moving body.
With the above-described conventional movement detector, when it is required to detect the movement of a moving body with high resolution, the detection may be achieved if the angular interval of the light transmitting parts or the light intercepting parts is decreased. However, in this case, it is essential to eliminate the interference of light between adjacent light transmitting parts. For this purpose, it is necessary to use a precise light projecting optical system such as a precise lens. Hence, the conventional movement detector is rather difficult to design, and is accordingly high in manufacturing cost.